A novel salt formed by mixed-valence vanadium(IV, V) [(VO)(2)O(bpy)(2)(C2O4)(2)] anions and ferromagnetic [Cu-2(bpy)(4)(C2O4)] cations: Structure, spectroscopic characterization and magnetic properties

The new heterometallic, mixed-valence compound [Cu2(bpy)4(C2O4)][(VO)2O(bpy)2(C2O4)2]2·10H2O has been synthesized, its crystal structure determined and its spectroscopic characterization accomplished by means of solid-state vibrational (far and mid FTIR) spectroscopy. The title compound crystallises in the triclinic system, space group P1¯ (No. 2) [a = 13.488(5) A, b = 14.160(6) A, c = 15.829(9) A, α = 87.22(2)°, β = 66.33(2)°, γ = 64.49(2)°, V = 2471(2) A3, Z = 1]. The compound consists of the cationic binuclear copper(II) complex [Cu2(bpy)4(C2O4)]2+, two anionic binuclear mixed valence vanadium(IV)−vanadium(V) complexes [(VO)2O(bpy)2(C2O4)2]−, and ten uncoordinated water molecules. The copper atom exhibits a Jahn−Teller-distorted octahedral coordination. The vanadium atoms adopt a strongly distorted octahedral coordination and form a characteristic O=V−O−V=O moiety with a significantly bent V−O−V link. The temperature dependence of the magnetic susceptibilities has been investigated in the temperature range 2−300 K and explained in terms of the ferromagnetic interaction between CuII ions giving J = 22.7 yJ (1.14 cm−1) and g = 2.014.